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 ###Instrução: Quantos líderes existem na classificação do intergiro na etapa 20?
 ###Tabelas: CREATE TABLE classification_leadership (classification_leadership_id AUTO_INCREMENT PRIMARY KEY, Stage VARCHAR, Winner VARCHAR, General classification VARCHAR, Points classification VARCHAR, Mountains classification VARCHAR, Young rider classification VARCHAR, Intergiro classification VARCHAR, Trofeo Fast Team VARCHAR) CREATE TABLE 1993 (1993_id AUTO_INCREMENT PRIMARY KEY, Overall Episode # INT, Original airdate VARCHAR, Iron Chef VARCHAR, Challenger VARCHAR, Challenger Specialty VARCHAR, Theme Ingredient VARCHAR, Winner VARCHAR) CREATE TABLE negotiation_progress (negotiation_progress_id AUTO_INCREMENT PRIMARY KEY, Screening Started VARCHAR, Screening Completed VARCHAR, Chapter Unfrozen VARCHAR, Chapter Opened VARCHAR, Chapter Closed VARCHAR) CREATE TABLE top_scorers_in_order_of_league_goals (top_scorers_in_order_of_league_goals_id AUTO_INCREMENT PRIMARY KEY, Player VARCHAR, Club VARCHAR, League INT, FA Cup INT, FA Trophy INT, League Cup INT, Total INT) CREATE TABLE great_northern_railway (great_northern_railway_id AUTO_INCREMENT PRIMARY KEY, Class VARCHAR, Type VARCHAR, Fleet numbers VARCHAR, Quantity made INT, Date made VARCHAR, 1958 CIÉ VARCHAR, 1958 UTA VARCHAR, Date withdrawn VARCHAR)  
SELECT COUNT Intergiro classification FROM classification_leadership WHERE Stage = 20